UV light sources have a variety of applications including: medical uses such as disinfection and sterilization; analytic uses utilizing change in irradiated UV light; industrial uses such as UV curing; cosmetic uses such as UV tanning; insect trap; counterfeit currency check, etc.
Traditionally, UV light source lamps used as such UV light sources include mercury lamps, excimer lamps, deuterium lamps, etc. Unfortunately, such existing lamps have problems in that they have high power consumption, generate much heat, have a short lifespan, and result in environmental contamination due to toxic gases filling therein.
In light of the above-described problems, UV LEDs are attracting attention as a solution for such problems. UV LEDs have advantages in that they have low power consumption and do not result in environmental contamination. However, manufacturing cost for an LED package emitting light in the UV range is much higher than that of an LED package emitting light in the visible range. In addition, UV light has unique characteristics, and thus it is difficult to develop various applications using an LED package.
For example, in order to manufacture lamp products using UV LEDs, the following issues have to be considered. One of the issues relates to a diffusion unit. In order to manufacture be a lamp using UV LED chips, a diffusion unit is required that is made of an appropriate transparent material such that it covers and protect the UV LED chips and transmits UV light. If the diffusion unit is made of quartz (glass), although it can transmit UV light of a single wavelength, it has to be handled with care since it is easily broken. In addition, such a diffusion unit has poor formability and low dissipation performance.
In view of this, a polymer that has better formability, is easier to handle and has better durability than quartz may be contemplated. However, a polymer exhibits low light transmittance since light having a wavelength of 400 nm or less (ultraviolet wavelength range) is absorbed by electron cloud which exists around a nuclear core and having a resonant frequency corresponding to that of UV. In addition, a diffusion unit made of a polymer itself may deteriorate by UV light. Thus, a polymer is not an appropriate material for a diffusion unit. In this regard, it is known that pure poly methyl methacrylate (PMMA) consists primarily of carbon and hydrogen and thus rarely has electron cloud, such that it exhibits high UV transmittance.
Another of the issues relates to the light distribution characteristics of LEDs. A pure PMMA, mentioned above, is a transparent material, and thus light sources and circuit parts disposed in a diffusion unit made of a pure PMMA is visible by observers, harming the aesthetic appearance. In addition, the center portion of the light source looks brighter due to the light distribution characteristics of LEDs, and thus it is difficult to achieve even illumination. If LEDs are disposed more densely in order to achieve even illumination, the cost of a UV LED light source device is greatly increased due to high price of a UV LED package.
In addition, when a UV LED light source device is employed as a light source of an insect trap lamp, it cannot attract insects effectively due to a hot spot. Further, for commercial uses such as UV curing or cosmetic uses such as tanning, a surface light source providing even UV illumination is preferred to point light sources. Accordingly, it is increasingly required to implement a UV LED lamp as a surface light source.